Characterization of Reference Gold Catalysts
Akihiko Yamaguchi, Masakazu Daté, Masatake Haruta,
As gold catalysts are becoming popular not only in the academic field, but also in the industry, World Gold Council, London (WGC) has started a project to supply standard gold catalysts. The reference gold catalysts are produced on the test plant scale by Süd-Chemie Catalysts Japan, Inc. under license of National Institute of Advanced Industrial Science and Technology (AIST). Authors participate in this project to carry out the characterizations and evaluations of these catalysts. In this paper, we will summary the characterizations of three kinds of reference gold catalysts, i.e., 5wt% Au/Fe2O3, 3wt% Au/TiO2, and 0.3wt% Au/Fe2O3/AUS (alimina beads).
1) Catalyst preparations and characterizations
Au/Fe2O3 and Au/TiO2 catalysts samples were successively produced on a large scale by Süd-Chemie Catalysts. The numbers of samples was 13 for both and the weight of each sample was 400 g. 500 ml of Au/Fe2O3/AUS sample was also produced by Süd-Chemie Catalysts. The actual loading of gold in the catalysts samples were determined by ICP (inductively coupled plasma) spectroscopy. The average diameter and their distributions of gold nano-particles were calculated from TEM (H-9000, Hitachi, Ltd.) photographs over about 100–200 particles, using the image analyzer.
2) Catalytic activity test
Catalytic activities of the samples were measured by using a fixed-bed flow reactor. Reactant gases of 1 vol% CO and H2 in air were fed at 1 atm in the space velocity of 20,000 ml/h/g-cat. The effluent gases were analyzed using a TCD gas chromatograph (GC-8A, Shimadzu Corporation). Prior to the measurements, the samples were heated in air stream at 523 K for 30 min.
Results and Discussion
Summary of the characterizations of 5wt% Au/Fe2O3 is listed in the next page. Activities of the catalyst samples are high enough compared to those prepared on a laboratory scale and are reproducible except for the top two samples (Au-Fe#01 and #02). The exception can be explained by the amount of residual Na, which was reduced to about tenth by further washing of the sample during the preparation after Au-Fe#03. The reproducibility in not only the chemical component and particle size of gold, but also catalytic activities indicates that these samples are suitable for the reference gold catalyst of the WGC project. In addition, the higher activities of the samples for CO oxidation than that for H2 oxidation, which is in good agreement with the samples prepared on a laboratory scale, confirms the success in expansion of the preparation scale. Results of the other samples, i.e., 3wt% Au/TiO2 and 0.3wt% Au/Fe2O3/AUS will be reported in the presentation.
Au/Fe2O3/AUS, Reference Gold Catalyst, Supported Gold Catalyst, Au/Fe2O3, Au/TiO2, Characterization